Biomechanical and radiographic comparison of demineralized bone matrix, and a coralline hydroxyapatite in a rabbit spinal fusion model.

The use of bone grafts is an essential component in spinal fusion. Autologous bone has been shown to result in long-term stable arthrodesis between spinal motion segments. However, autograft can be associated with significant morbidity and a limited supply. Alternatives, such as allogeneic demineralized bone matrix (DBM), are a potential source and supplement to autograft bone. The current study compares the ability of a DBM product (BioSet RT) and a coralline hydroxyapatite (Pro Osteon 500R), for inducing spinal fusion in a rabbit model. BioSet RT, alone or in combination with autograft, and Pro Osteon 500R were implanted in the posterior lateral inter-transverse process region of the rabbit spine. The spines were evaluated at 18 weeks for fusion of the L4-L5 transverse processes using a total of 33 skeletally mature male rabbits; 4 naïve animals were also included in the study. Samples were evaluated radiographically, histologically, by palpation, and through mechanical strength testing. Radiographical, histological, and palpation measurements demonstrated the ability of BioSet RT to induce new bone formation and bridging fusion comparable to autograft. This material performed well alone or in combination with autograft material. Despite significantly higher biomechanical testing results, minimal bone formation and fusion was recorded for the Pro Osteon 500R-treated group. This in vivo study demonstrates the ability of BioSet RT to induce new bone formation, and there was a clear relationship between bridging bone and mechanical strength.

Histological and radiographic evaluations of demineralized bone matrix and coralline hydroxyapatite in the rabbit tibia.

Complex fractures resulting in bone loss or impaired fracture healing remain problematic in trauma and orthopedic surgeries. Many bone graft substitutes have been developed and are commercially available. These products differ in their osteoconductive and osteoinductive properties. Differential enhancement of these properties may optimize the performance of these products for various orthopedic and craniofacial applications. The use of bone graft substitutes offers the ability to lessen the possible morbidity of the harvest site in autografts. The objective of the present study was to compare the ability of two bone graft substitutes, BioSet RT, an allograft demineralized bone matrix formulation, and ProOsteon 500R, a coralline hydroxyapatite, in a rabbit critical tibial defect model. BioSet RT and ProOsteon 500R were implanted into a unicortical proximal metaphyseal tibial defect and evaluated for new bone formation. Samples were analyzed radiographically and histologically at 1 day, 6 weeks, 12 weeks, and 24 weeks post surgery. Both materials were biocompatible and demonstrated significant bone growth and remodeling. At 12 weeks, the BioSet RT implanted sites demonstrated significantly more defect closure and bone remodeling as determined by radiographic analyses with 10 out of 14 defects being completely healed versus 1 out of 14 being completely healed in the ProOsteon 500R implanted sites. At 24 weeks, both materials demonstrated complete closure of the defect as determined histologically. There were no statistical differences in radiographic scores between the two implanted materials. However, there was an observable trend that the BioSet RT material generated higher histological and radiographic scores, although not statistically significant. This study provides evidence that both BioSet RT and ProOsteon 500R are biocompatible and able to induce new bone formation as measured in this rabbit model. In addition, this in vivo study demonstrates the ability of BioSet RT to induce new bone formation in a shorter timeframe than ProOsteon 500R.